Mechanisms for excited state relaxation and dissociation of oxymyoglobin and carboxymyoglobin.

Abstract
The dissociation of [sperm whale] carboxymyoglobin (MbCO) and oxymyoglobin (MbO2) induced by 530 nm picosecond excitation in the .beta. band or the 355 nm .delta. band was measured by monitoring the absorbance changes at 420 and 440 nm corresponding to ligand-bound and ligand-detached species, respectively. MbO2 and MbCO dissociate with very similar rates, which do not reflect the 30-fold difference between the quantum yields of the 2 reactions. Kinetic data suggest that a short-lived intermediate is formed that is responsible for the low quantum efficiency of the MbO2 dissociation.